1. Field of the Invention
This invention relates in general to computer systems, and more specifically to a printed circuit board for a portable computer.
2. Description of the Related Art
Personal computer systems have attained widespread use. A personal computer system can usually be defined as a desktop or portable microcomputer that includes a system unit having a system processor or central processing unit (CPU) with associated memory, a display panel, a keyboard, a hard disk storage device or other type of storage media such as a floppy disk drive or a compact disk read only memory (CD ROM) drive. These personal computer systems are information handling systems which are designed primarily to give independent computing power to a single user or group of users.
A portable computer is a self-contained personal computer designed to be easily moved to and operated in various locations. Portable computers are often referred to as laptop, notebook or subnotebook computers. To be portable, these computers are small, compact, and lightweight. The conventional portable computer has a base portion and a lid portion that pivotally opens from the base portion. The lid portion contains a flat panel display such as a liquid crystal display (LCD) or other relatively thin display.
To generate an image on the display of a portable computer, electrical signal and power are provided from the base. The mechanism to allow this must be stable and robust enough to withstand thousands of opening and closing cycles without showing degradation of performance. Currently, many portable computers use flexible printed circuit boards with multiple electrical conductive circuit traces embedded in the flexible circuit boards to connect the base portion of the computer to the display portion. On one end of the flexible circuit are the connections to a motherboard in the base. The other end of the flexible circuit includes connections to an LCD screen, the inverter board for the back light, and several LED displays which indicate the operational status of the computer.
In some portable computers, the flexible circuit is adhered to and wrapped inside and around a tubular bobbin device. Repeated opening and closing of the hinged top wraps and unwraps the flexible circuit around the bobbin. The bobbin method is particularly susceptible to stress concentrations resulting from improper assembly of the flexible circuit to the bobbin. Variations in circuit assembly can vary the life of the flexible circuit by an order of magnitude. Furthermore, shielding must be supplied around the flexible circuit to protect against electromagnetic interference (EMI) with high-speed video signals such as Low Voltage Differential Signaling (LVDS) signals. Such shielding is generally supplied by a copper or other shielding medium externally encasing the electrically conductive signals between the base portion and the display portion. In bobbin-wound flexible circuit connections, the copper shielding might be external to the flexible circuit but inside the bobbin to keep the copper shielding in place. This creates an extra step in the manufacturing of the notebook computer.
In other portable computers, the flexible circuit is passed from the computer base to the display by passing it through a protected area in a flat configuration so that the circuit bends unidirectionally. The severe bending at particular points along the flexible length of the flexible circuit make this method more susceptible to stress concentrations. Reliability is substantially affected by changes over time to the circuit's physical geometry. Like the bobbin-wound circuit, a straight pass-through flexible circuit requires EMI sheilding.
What is needed is a standardized flexible circuit able to reliably withstand thousands of rotations of the lid portion without variance of performance due to assembly techniques that is more robust than either the straight pass method or the bobbin wound method. Further, a standardized flexible circuit is needed that incorporates EMI shielding without requiring further steps in manufacturing.